For example, KR20090084753A discloses a spool control valve that has a solenoid actuator (hereinafter referred to as a solenoid) 200, as shown in FIG. 13. The solenoid 200 drives a spool valve 101, which is a valve element of the spool control valve, toward an adjust screw 104 in a spool hole 103 of a sleeve 102 (i.e., toward an opening of the spool hole 103) against an urging force of a return spring 120.
The solenoid 200 includes a coil 106, a stator core (a radially-inner-side stationary core) 107, a yoke (a radially-outer-side stationary core) 108 and a plunger 109. The coil 106 is wound around a bobbin 105 that is made of a synthetic resin material. The stator core 107 is configured into a cylindrical tubular form and is placed on a radially inner side of the coil 106. The yoke 108 is configured into a cylindrical tubular cup form and is placed on a radially outer side of the coil 106. The plunger 109 is movable in an inside of the stator core 107.
Furthermore, the solenoid 200 includes two primary terminals 111, two secondary terminals 112 and a holder 113. The primary terminals 111 and the secondary terminals 112 are used to supply an electric power to the coil 106. The holder 113 has a function of a connector case, to which an external mating connector is fitted.
Each of the primary terminals 111 is used as a coil terminal (a terminal at the coil side) and includes an inner connection and a primary intermediate connection. The inner connection of each primary terminal 111 is joined to a corresponding conductor body (a conductor line), which forms the coil 106. The primary intermediate connection of each primary terminal 111 is joined to and is electrically connected to a corresponding one of the secondary terminals 112.
Each of the secondary terminals 112 is used as an external side coil terminal and includes an outer connection (a tuning fork terminal portion) and a secondary intermediate connection. The outer connection of each secondary terminal 112 is fitted to an outer connection (a tab terminal portion) of a corresponding one of two external mating terminals of the external mating connector. The secondary intermediate connection of each secondary terminal 112 is joined to and is electrically connected to the primary intermediate connection of the corresponding primary terminal 111 by, for example, welding or crimping.
In the solenoid 200, a distal end portion (a snap fit claw 117) of a resilient engaging piece 116, which projects from the holder 113 through a through-hole 115 formed in a bottom portion 114 of the yoke 108, is snap fitted to an engaging part 118, which is formed in an inner surface of the bottom portion 114 of the yoke 108, so that the holder 113 is snap fitted to an outer surface of the bottom portion 114 of the yoke 108. Since the fixing method of the holder 113 relative to the outer surface of the bottom portion 114 of the yoke 108 is the snap fitting, rattling will occur at the snap fit connection between the snap fit claw 117 of the resilient engaging piece 116 and the engaging part 118 of the bottom portion 114. At the time of occurrence of the rattling at the snap fit connection, a positional deviation may occur between the primary intermediate connection of each primary terminal 111 and the secondary intermediate connection of the corresponding secondary terminal 112, and a positional deviation may also occur between the outer connection of each secondary terminal 112 and the outer connection of the corresponding external mating terminal. Therefore, there is a difficulty with respect to achievement of a required reliability of the electrical connection at the primary and secondary intermediate connections and a required reliability of the electrical connection at the outer connections.
In view of the above disadvantage, in order to achieve the required reliability of the electrical connection at the primary and secondary intermediate connections of the primary and secondary terminals and a required reliability of the electrical connection at the outer connections of the secondary terminal and the external mating terminal, the inventors of the present application have previously proposed and tested a linear solenoid (comparative example) shown in FIGS. 14 to 15B.
In the linear solenoid of the comparative example shown in FIGS. 14 to 15B, two of terminals, each of which includes the inner connection and the outer connection formed integrally together in the terminal, are used in place of the primary and secondary terminals of the prior art solenoid. Therefore, it is possible to eliminate the connecting structure between each primary terminal and the corresponding secondary terminal and the connecting operation for connecting between each primary terminal and the corresponding secondary terminal.
In the linear solenoid of the comparative example, with reference to FIG. 14, the following method is used as a fixing method for fixing a terminal holder (hereinafter referred to as a holder) 121, which receives and holds the terminals discussed above, to an outer surface (a holder installation seat surface 119) of the bottom portion 114 of the yoke 108.
Specifically, in the linear solenoid of the comparative example, an inside-to-outside communication hole is formed in the bottom portion 114 of the yoke 108, which is configured into the cylindrical tubular cup form. Furthermore, the terminals are projected from an inside to an outside of the yoke 108 through the inside-to-outside communication hole of the bottom portion 114, and two positioning projections 122 project from the holder installation seat surface 119 of the bottom portion 114 of the yoke 108 to the outside of the yoke 108.
A fitting hole 124 is formed at a center portion of each of two flanges 123 of the holder 121. The positioning projections 122 are fitted into the fitting holes 124, respectively, to position the holder 121 in a predetermined position in the holder installation seat surface 119. Thereafter, an engaging hole 126 of a clip 125, which is made of a resiliently deformable thin metal plate, is press fitted to each of the positioning projections 122.
Specifically, as shown in FIG. 15A, at the time of press fitting the clip 125 to the corresponding positioning projection 122, a press fitting load is applied to the clip 125 to resiliently contact the clip 125 to both of the flange 123 and the positioning projection 122. Then, after the press fitting of the clip 125 to the corresponding positioning projection 122, a yoke contact surface 127 of the holder 121 is urged toward the bottom portion 114 of the yoke 108 through use of a resilient restoring force of the clip 125, so that the yoke contact surface 127 of the holder 121 fluid-tightly contacts the holder installation seat surface 119 of the bottom portion 114 of the yoke 108.
The linear solenoid of the comparative example has a foreign object intrusion limiting function. Specifically, since the yoke contact surface 127 of the holder 121 fluid-tightly contacts the outer surface of the bottom portion 114 of the yoke 108, it is possible to limit intrusion of the foreign objects, such as conductive foreign particles (particulate contaminants), into the inside of the yoke 108 through the inside-to-outside communication hole of the bottom portion 114.
Furthermore, two tapered guide surfaces 132 are formed in each of two terminal insertion holes 131, through which the tab terminal portions of the external mating terminals are inserted into terminal receiving chambers of the holder 121. Therefore, at the time of fitting the external mating connector to the holder 121, the tab terminal portions of the external mating terminals can be easily inserted into the terminal receiving chambers, respectively.
However, in the case of the linear solenoid of the comparative example, the clip 125 may possibly be sprung back after the press fitting of the clip 125 to the corresponding positioning projection 122, so that the clip 125 may possibly be lifted away from an installation seat surface of the corresponding flange 123 of the holder 121, as indicated in FIG. 15B.
When this phenomenon occurs, a clearance is formed between the flange 123 and the clip 125 to cause formation of a gap between the yoke contact surface 127 of the holder 121 and the outer surface of the bottom portion 114 of the yoke 108. Thereby, the foreign object intrusion limiting function discussed above may possibly be lost.